Check all of the cables for loose connections, check that the LED power indicator on speaker is on. Go to CONTORL PANEL > AUDIO DEVICES, make sure MUTE is not on. And try moving the volume slider to see if it makes any difference (slider should be at maximum). Also check for headphones which may be plugged into any ports and if all this is not the problem. Switch off computer, open the case and check that all PCI cards are slotted in properly. If you have MSN Messenger, go to TOOLS > AUDIO/VIDEO TUNING WIZARD. Complete the wizard and usee the TEST SPEAKERS function to check that your speakers are not working.